Consistent with conrad-johnson's design philosophy that circuits should be kept as simple as possible, these amplifiers work their magic with a minimum of vacuum tubes (six in the mono LP125M). A composite triode input stage is direct coupled to a cathode-coupled phase inverter. The output stage is comprised of 6550s operated in ultra linear configuration (two pair for the LP125M) for an optimal combination of high power and low distortion. Limited negative feedback is applied to the circuit to reduce distortion and provide a sufficiently high damping factor to control most real-world speaker systems. Discrete dc power supply regulators are provided for the input and inverter stages, in order to isolate each stage from the output signal.
As with all conrad-johnson tube amplifiers, these amplifiers require no complicated adjustments or specialized equipment to maintain. To assure continued peak performance, the owner need only make a simple bias adjustment when new tubes are installed. Built in LED bias indicators allow the user to make this adjustment using only the supplied screwdriver.
Component parts quality is signature strength of any conrad-johnson product. The audio circuit and related power supplies feature precision metal film resistors and high-performance polypropylene capacitors. There are no electrolytic capacitors in the audio circuit or in the related power supplies. Proprietary wide-bandwidth output transformers contribute to excellent high frequency performance. Even the input/output connectors and internal wiring have been carefully selected for optimal sonic performance.
For those who do require more power, the LP125M mono-block delivers a solid 125 watts. Along with the tonal integrity and faithfulness to the music that are embodied in these amplifiers, their ease of use, low maintenance costs, and reliability will be a revelation for those who have only experienced "entry-level" tube gear.
